1. Field of the Invention
The field of art to which this invention relates is surgical instruments, in particular, electrosurgical cutting and grasping instruments.
2. Description of the Related Art
Two techniques used extensively in both open and endoscopic surgery are (a) the controlling of bleeding using electrosurgical instrumentation and (b) the incision or severing of tissue or vessels. The control of bleeding during surgery accounts for a major portion of the time involved in surgery. In particular, bleeding that occurs when tissue is incised or severed can obscure the surgeon's vision, prolong the operation, and adversely effect the precision of cutting. Blood loss from surgical cutting may require blood infusion, thereby increasing the risk of harm to the patient.
Hemostatic electrosurgical techniques are known in the art for reducing bleeding from incised tissue prior to, during, and subsequent to incision. Electrosurgical cutting and coagulating instruments are used to perform such techniques. These instruments can be of a reusable type (which require cleaning and disinfecting or sterilizing before each use) or disposable (which are disposed of after a single use). Each type includes both monopolar and bipolar variations having at least one electrode. Radio frequency (RF) energy is conducted through this electrode to either a remote conductive body-plate (known as a grounding pad) in the case of monopolar instruments, or to a second, closely spaced conductive electrode in the case of bipolar instruments. In monopolar instruments electrical current travels from the electrode through the patient's body to the grounding pad. Bipolar instruments are typically connected to both poles of an electrosurgical generator, therefore current flow is typically limited to tissue adjacent to the working end of the bipolar instrument (where the two electrodes are located).
Standard shape and size scissors have evolved in the surgical arts which surgeons have become accustomed to. These standards have been incorporated into the electrosurgical scissors, not only because they have been tested by time and found to be very functional, but mainly because surgeons have become accustomed with their feel and use. Examples of some of these standards include the Mayo, Metzenbaum, and Tenotomy scissors. Each standard scissor is typically available in both curved and straight variations.
Recent research and post-market surgical use has indicated the need for variations of these standard shape and size electrosurgical scissors, preferably of the bipolar variety. Current standard shape and size electrosurgical scissors include: 41/2" Tenotomy; 7", 9" and 11" Metzenbaum; and 63/4" Mayo styles. These scissors were developed to fit general scissor requirements for general, GYN and plastic surgical procedures. The technology has been well received, and evaluations of the scissors have expanded to the surgical specialties of otolaryngology, ENT, vascular, cardiovascular, urology, thoracic, neurology and pediatric surgery. This expansion into additional surgical specialties has opened the need for additional variations which will more closely replicate the existing style or size of the standard surgical scissors in current use. Research indicates that additional scissor variations are needed to take advantage of current trends in procedural usage. Some proposed scissor styles, ranked in descending order for proposed greatest use, include: 7", 9" fine-tip Metzenbaum, 7" Tenotomy, 9" Mayo, 11" fine-tip Metzenbaum and a 51/2" fine-tip Metzenbaum. The addition of a fine-tip Metzenbaum (51/2", 7", 9", 11"), a 7" Tenotomy and a 9" Mayo allows for expansion into additional surgical specialties or specific procedures.
In addition to these variations, it is also desired to modify the amount or length of electrical insulation distally toward the scissor tips. This would increase the amount of electrical insulation on the blades, therefore, decreasing the zone where current or thermal effect could be delivered. This would make the scissor easier to use and would allow surgeons to work closer to delicate structures with increased comfort and control. This enhancement has particular benefits in procedures involving close work to sensitive structures such as otorhinolaryngology or plastic procedures (e.g., tonsillectomies, facelifts, blepharoplasties, tram flaps, free flaps, laryngectomies, thyroidectomies), general procedures (e.g., carotidectomies, carotid enarterectomy, radical neck dissections for CA), and CV/vascular/thoracic procedures (e.g., CABG IMA harvest and/or saphenous vein, mitral or aortic valve replacement, congenital defect repairs, femoral popliteal or tibular bypass, abdominal aortic aneurysm, lung biopsy, thoracotomy, wedge resection).
The configuration of the insulating coating on the blades of the bipolar scissors has been a design criterion since the conception of bipolar scissors. To understand its relevance, a brief discussion of how the scissors function will be helpful.
With bipolar scissors, a first blade is the first active electrode and is disposed at the distal end of a first handle. The second blade is the second electrode of opposite polarity and is disposed at the distal end of a second handle. One of the first and second blades is insulated from the other blade by a first insulating coating, preferably aluminum oxide, on the shearing surface, i.e., the cutting edge of the blade and by a second insulating coating, also preferably aluminum oxide, on the pivot screw. A third insulating coating is disposed on the handles, including the area around the pivot screw and on a "portion" of the non-shearing, outside surfaces of the blades. The electrical insulation provides electrical insulation to prevent passage of electrical RF current, so that these insulated areas can contact non-targeted patient tissue, or be touched by the surgeon or surgical assistants. When the scissors are activated, the path of RF current is through the targeted tissue that is in contact with the uninsulated portions of the blades. The surgeon can control the amount of tissue that is exposed to RF energy and the portion of an uninsulated blade surface exposed to the tissue.
In standard electrosurgical scissors, the configuration of the electrical insulation was such that the exposed or uninsulated surface of both blades was defined by the length of blade that was ground to produce the cutting edge. This would allow the surgeon to utilize the full range of that "cutting-area" to effect coagulation of tissue. While the standard electrosurgical scissors of the prior art have their advantages, in surgical procedures performed in confined areas or in delicate anatomy, they can lead to cauterization of unintended tissue.
Accordingly, there is a need in the art for an improved electrosurgical instrument designed for procedures involving close work to sensitive structures and which remain in a standard scissor shape and size.